adjusting timing on boosted lt1

[supr67]

I just finished my turbo lt1 build trying to get the timing set right. If any one has a .cal file to compare would be real helpfull but any advice would be great right now im running max advance of 28 degrees in boost.

[RobertISaar]

what year PCM are you playing with? i assume 96-97?

i've patched a DA2 or DA3 BIN for boost support before, it could be done for EE as well, but i haven't needed to play with the 96/97 setup before.

[supr67]

sorry for the long wait been super busy and yes it is a obd 2 96 pcm and I am new to tuning i have managed to get the timing close now i am dialing in my injectors I have ford green top 42 lb injectors and cant seem to find any info on offset tables for the lt1.

[mekkis]

What blower, boost level, etc?

[supr67]

What blower, boost level, etc?

Turbod at nine pounds right now

[steveo]

i've always wondered, how the hell do you adjust timing for something that creates manifold pressure above the limit of the ECM's timing table?

do you just do all your timing @ atmospheric and have it flat in boost?

just curious.

[mekkis]

It's pretty common to run the 94-97 LT1s in speed density, plug in a 2 bar MAP, lower the baro update, and go for it. 50kpa in the logs is really 100kpa, etc.

OP, I'm trying to dig up an LT1 tune I did on an STS car, but it's not falling to hand. Off the top of my head a blower car in your boost range would like 29-31* range, but turbo cars generally want less timing due to all the drive pressure keeping the exhaust valves and head warmer.

[supr67]

Yea I'm real close to thirty one now and any info on those injectors would also be really handy

[RobertISaar]

It's pretty common to run the 94-97 LT1s in speed density, plug in a 2 bar MAP, lower the baro update, and go for it. 50kpa in the logs is really 100kpa, etc.

that seems like it would cause far more problems than just barometric calcs.

[mekkis]

that seems like it would cause far more problems than just barometric calcs.

Yeah, I suggest Holley HP/Dominator, but I don't choose what comes on or is done with 95% of the cars I work on.

Anyway, if you've not seen it before: http://www.camaroz28.com/forums/computer-diagnostics-tuning-36/2-bar-stock-pcm-speed-density-tune-6psi-forced-induction-560089/

[delcowizzid]

i normally drop 1 degree-1.5 degrees per psi off my 100kpa timing curve but it depends on your fuel ratio i run 11.8:1 fueling on boost .if your real rich it will handle more timing but rich costs power.i could run way leaner and make more power but i like to stay a little rich just to cover any cylinders that may be running leaner than others since fuel ratio measured in the pipes is an average of all cylinders and one could be rich and one could be lean and still give you good a/f readings.

[MYLTWON]

Could someone please explain to me how lowering the baro update update gives you a bigger range to measure in the computer?

[RobertISaar]

that alone doesn't. modifying when the baro value can be calculated prevents the PCM from adjusting baro up to whatever boost you're running in the real-world while it thinks it is actually still in the 1BAR range. expect other "funny" things to happen though, considering in a normal situation, the PCM will be calculating somewhere along the lines of 50kPa barometric.